1. Field of the invention
The invention relates to a beat treatment device of the light irradiation type in which a semiconductor wafer (hereinafter called a wafer) is heated by light for layer formation, diffusion, baking and the like.
2. Description of Related Art
Heat treatment of the light irradiation type in the manufacture of semiconductors is conventionally done in broad areas, such as layer formation, diffusion, baking and the like.
In any of these treatments, a wafer is heated to a high temperature and treated. The wafer can be quickly heated by light irradiation. The temperature of the wafer can be raised after a dozen to a few dozen seconds to at least 1000xc2x0 C. Furthermore, prompt cooling of the wafer can be achieved when light irradiation is stopped.
A conventional device for heat treatment of the light irradiation type is known, for example, in Japanese patent disclosure document HEI 6-93440 (U.S. Pat. No. 5,155,336). In FIG. 1 shows this device. In this figure, a light irradiation chamber 1 is divided by a silica glass window 8 and a wafer 3 is seated on a wafer holding plate 2 for being subjected to heat treatment. The silica glass window 8 is used when the atmosphere in the vicinity of the wafer 3 and the atmosphere in the vicinity of the lamp 4 are different.
Above the silica glass window 8, there are several IR lamps 4 next to one another with a unilateral hermetic seal in a sealing area 6 located on only one end of the lamp. Each lamp 4 is inserted into an optical guide 5 in a state in which the vicinity of its sealing area 6 is supported by a wall 9. A cooling liquid is introduced into the spaces which are formed by the wall 9 and the optical guide 5, each of which forms a respective cooling chamber 7.
When power is supplied to the respective lamp 4, the filament within the lamp 4 emits light. The light is reflected by an inner reflective side of the respective optical guide 5 of stainless steel or the like and is radiated onto the wafer 3 on the wafer holding plate 2 of the light irradiation chamber 1, causing the wafer 3 to be heated. The cooling liquid in the respective cooling chamber 7 cools such that the temperature of the optical guide 5 and of the sealing area 6 of the lamp 4 is not unduly increased by the radiant energy from the lamp 4.
But in this conventional example, it was possible to cool only the optical guides 5 and the sealing areas 6, because there the optical guides 5 and the sealing areas 6 are cooled using heat conduction by the cooling liquid which flows in the cooling chambers 7. The emission part (the silica glass area surrounding the filament) of the lamp 4 could not be adequately cooled in this way.
If the power supplied to the lamps 4 is increased in order to raise the rate of the temperature increase of the wafer to increase the throughput and to shorten the treatment time, there are, therefore, cases in which the temperature of the silica glass which forms the respective emission portion of the lamp 4 rises and reaches a temperature of at least 1000xc2x0 C.
At a temperature of the silica glass used for the respective emission portion of at least 800xc2x0 C., recrystallization of the silica glass occurs, as does milky opacification which is called xe2x80x9cdevitrification.xe2x80x9d When the temperature of the lamps 4 rises and devitrification of the silica glass occurs, the light from the filaments passes only poorly through the silica glass. The stipulated light energy from the lamps 4 can no longer be radiated onto the wafer 3. As a result, there were cases in which the device did not work effectively as a heating device.
The invention was devised to eliminate the above described defect in the prior art. Therefore, a first object of the invention is to devise a heat treatment device of the light irradiation type with a long service life in which effective, adequate cooling of the lamps prevents devitrification of the lamp emission portion, even if the power supplied to the lamp is increased to accelerate the temperature increase of the wafer.
A second object of the invention is to devise a heat treatment device of the light irradiation type in which the lamps can be cooled effectively and adequately and the number of lamps per unit of area can be increased to accelerate the temperature increase of the wafer.
A third object of the invention is to devise a heat treatment device of the light irradiation type with a long service life, in which the light energy can be effectively used by preventing a temperature increase of the sealing areas of the lamps.
The objects are achieved as claimed in the invention as follows:
A heat treatment device of the light irradiation type in which light is radiated from lamps and thus heating takes place comprises the following:
a mirror in which several lamps with a unilateral hermetic seal located next to one another;
air injection lines for cooling air located in the above described mirror for cooling of these several lamps; and
at least one air exhaust line for blowing out the above described cooling air which has been blown in.
Furthermore, the objects are achieved in the above described heat treatment device of the light irradiation type in that the above described at least one air exhaust line is located in the above described mirror in order to blow out the above described cooling air from the vicinity of the lamps.
Moreover, the objects are achieved in the above described heat treatment device of the light irradiation type in that the lamps are located in a lamp chamber which surrounds the above described mirror and there is at least one air exhaust line in one side wall of the lamp chamber.
In addition, the objects are achieved in the above described heat treatment device of the light irradiation type in that the air exhaust line is comprised of several air lines which surround the outside peripheral surfaces of the lamps.
Furthermore, the objects are achieved in the above described heat treatment device of the light irradiation type in that there is a reflection component between the filament and the sealing area in the lamps.
In the following the invention is specifically described using several embodiments which are shown in the drawings.